The University of Queensland, Center for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia; School of Food and Biological Engineering, Jiangsu University, Zhenjiang, Jiangsu Province 212013, China.
The University of Queensland, Center for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane, QLD 4072, Australia; Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia.
Carbohydr Polym. 2022 Nov 1;295:119871. doi: 10.1016/j.carbpol.2022.119871. Epub 2022 Jul 16.
To elucidate starch structural features underlying resistant starch formation, wheat starch granules with three (A-, B- and C- type) crystalline polymorphisms and a range of amylose contents were digested in vitro. The changes in multi-level structure of digestion residues were compared. In the residues of A- and C-type starches, the molecular fine structure (distributions of chain length and whole molecular size), as analyzed by size exclusion chromatography (SEC), remained similar during digestion. In contrast, B-type high amylose wheat starch (HAWS) showed distinct changes in multi-level structures of digestion-resistant fractions: (1) the peak of longer amylopectin branches shifted to a lower degree of polymerization (40 DP); (2) production of α-limit dextrin (~2 nm hydrodynamic radius) in the residues; (3) a small increase of double helix content during digestion, in contrast to 6 % reduction for the A-type starch; (4) a decrease (6 °C lower) in the melting temperature of amylose-lipid complexes. The comparison suggests that elongated branches in B-type starch contribute to the formation of resistant fraction (including α-limit dextrin) against α-amylase. The amorphous packing of starch polymers with elongated branches together with the absence of surface pores and channels is proposed to be the basis for the enzymatic resistance of granular HAWS.
为了阐明抗性淀粉形成的淀粉结构特征,我们用体外消化的方法研究了具有三种(A、B 和 C 型)晶型多态性和不同直链淀粉含量的小麦淀粉颗粒。比较了消化残留物多层次结构的变化。在 A 型和 C 型淀粉残留物中,通过尺寸排阻色谱(SEC)分析的分子精细结构(链长和整个分子大小的分布)在消化过程中保持相似。相比之下,B 型高直链小麦淀粉(HAWS)在抗消化部分的多层次结构中表现出明显的变化:(1)更长的支链淀粉支链的峰值向聚合度较低的方向移动(40 DP);(2)在残留物中产生α-极限糊精(~2 nm 水动力半径);(3)在消化过程中双螺旋含量略有增加,而 A 型淀粉则减少 6%;(4)直链淀粉-脂质复合物的熔融温度降低(6°C)。比较表明,B 型淀粉中长支链的存在有助于形成抗消化部分(包括α-极限糊精),抵御α-淀粉酶的作用。淀粉聚合物长支链的无定形堆积以及缺乏表面孔隙和通道被认为是颗粒状 HAWS 酶抗性的基础。